Production of colored photographic images by the silver dye bleach process

ABSTRACT

SILVER DYE BLEACHING PROCESS UTILIZING SILVER HALIDE EMULSIONS IN WHICH THE MOLAR RATIO OF SILVER TO THE BLEACHABLE AZO GROUPS OF THE AZO DYE IS AT LEAST 12 TO 1 AND DEVELOPMENT IS CARRIED OUT WITH A DEVELOPER OF THE P-PHENYLENEDIAMINE SERIES HAVING A HIGH SULFITE CONTENT. THIS INVENTION RELATES TO A PHOTOGRAPHIC MATERIAL AND TO A PROCESS FOR THE PRODUCTION OF COLORED PHOTOGRAPHIC IMAGES BY THE SILVER DYE BLEACHING PROCESS. IT IS KNOWN TO PRODUCE COLORED PHOTOGRAPHIC IMAGES BY THE SILVER DYE PROCESS. IN THIS PROCESS, THE DYE (OR DYES IN THE CASE OF A MULTI-LAYERED MATERIAL), WHICH IS USUALLY AN AZO DYE, IN A HOMOGENEOUSLY DYED COLLOIDAL LAYER IS BLEACHED IMAGEWISE IN A STRONGLY ACID BATH IN THOSE AREAS OF THE LAYER WHERE A SILVER IMAGE HAS PREVIOUSLY BEEN PRODUCED.

United States Patent 01 hoe Patented June 15, 1971 PRODUCTION oFcoLoREi) PHOTO-GRAPHIC IMAGES BY THE SILVER DYE BLEACH PROCESS ErichBockly, Leverkusen, Justus Danhiiuser, Cologne- Stammheim, Max Heilmann,Cologne-Flittard, Johannes Giitze, Bergisch-Neukirchen, and EberhardGiinther, Leverkusen, Germany, assignors to Agfa-GevaertAktiengesellschaft, Leverkusen, Germany N Drawing. Filed Mar. 21, 1969,Ser. No. 809,407 Claims priority, application Germany, Apr. 4, 1968,

P 17 72 137.8 Int. Cl. G03c 7/00 U.S. Cl. 96-53 3 Claims ABSTRACT OF THEDISCLOSURE Silver dye bleaching process utilizing silver halideemulsions in which the molar ratio of silver to the bleachable azogroups of the azo dye is at least 12 to l and development is carried outwith a developer of the p-phenylenediamine series having a high sulfitecontent.

This invention relates to a photographic material and to a process forthe production of colored photographic images by the silver dyebleaching process.

It is known to produce colored photographic images by the silver dyebleaching process. In this process, the dye (or dyes in the case of amulti-layered material), which is usually an azo dye, in a homogeneouslydyed colloidal layer is bleached imagewise in a strongly acid bath inthose areas of the layer Where a silver image has previously beenproduced.

Both negative and reversal images can be produced by this process. Ifpositive images on paper or duplicate positives are to be produceddirectly from diapositives, a simple black-and-white development is usedto produce a silver image which is then a negative of the original usedfor copying. Since the dye which is homogeneously distributed in thelayer (or in three layers when using a multi-colored material) isdestroyed to the extent that the silver image is formed, the requireddye image re versal image) which is a positive of the original isfinally obtained. If a silver image, i.e. a silver reversal image, whichis a positive of the original is produced, e.g.. by a black-and-whitereversal development or by means of the bromine ion diffusion process, adye image which is 0pposite in gradation to the original is producedafter bleaching of the dye, i.e. a positive color image if the originalis a color negative.

Considerable diificulties arise in producing colored images by thesilver dye bleaching process which have a suificiently fine dye grainand sufliciently low gradation.

Another disadvantage of the silver dye bleaching proc ess is that theazo dyes contained in the silver halide emulsion layers absorb light ofthe particular wavelength region to which the silver halide issensitive. Hence the sensitivity of the layers is greatly reduced. Forthis reason, the known materials for uese in the silver dye bleachingprocess are only suitable for use as copying materials and even whenused for this purpose they are inferior to the conventional photographiccopying materials.

It is an object of the invention to modify the silver dye bleachingprocess by choosing certain silver halide emulsions and makingvariations of the process so that colored images which have a fine grainand low gradation can be obtained and so that a very high sensitivity ofthe silver halide emulsion layer is also obtained.

It has now been found that emulsions in which the molar ratio of silver(in the form of silver halide) to the bleachable azo groups of the azodye is at least 12:1 and which are developed with a developer of thephenylene diamine series at relatively high sulfite concentrations areparticulary suitable as photographic materials for use in the silver dyebleaching process.

It is desirable to use highly sensitive silver iodobromide gelatineemulsions. The ratio of silver to azo bond according to the invention of12:1 is far greater than the quantity of silver required for bleachingan azo bond according to the following equation:

The highly sensitive emulsions contain at least g. of silver, in theform of silver halide, per kg. of crude emulsion. It is especiallypreferred to use emulsions which have silver contents of to 30 of silverper kg. of crude emulsion, which corresponds to a silver dye ratio ofabout 16:1 to about :1 per azo bond, depending on the molecular weightof the azo dye used.

Development is carried out with a color forming developer of thep-phenylenediamine series, preferably one of the following:N,N-diethyl-p-phenylenediamine, compounds according to German patentspecification 965,617, 4-(N,N-diethylamino)-2-rnethylaniline or 4-(N-ethyl-N- methyl-sulfarnidoethyl-amino)-2-methylaniline. The concentration is generally between 0.5 and 25 g. per litre of developersolution, preferably between 2 g. and 15 g. per litre.

The sulfite content of the developer solution is substantially higherthan that of the developing compositions conventionally used for thecolor-forming development of color materials which have color couplersincorporated. Thus, instead of using'2.5 to 4.0 g. per litre, amounts ofabout 15 to 60 g. of sulfite are used per 1 litre of solution; it ispreferred to use 20 to g. These sulfite contents are very unusual andare undesirable when used for processing conventional color photographicmaterials (see the article by K. Meyer, Bild und Ton (1954) page 72).

If the silver dye bleaching materials described above are developed in aconventional black-and-white developer after exposure and then processedin the same manner, the gradations obtained with such an excess ofsilver halide are much too high and the dye grain is much coarser. Thematerials according to the invention are prepared in the usual manner.They are preferably cast on supports which have a very smooth surface,e.g. pigmented cellulose acetate foils.

The silver halide emulsion layers may be optically and chemicallysensitized in known manner. They may contain the known azo dyes, e.g.those described in the following German Pats. 1,284,299; 1,285,308;German patent specification P/15/22/354.8; French Pat. 1,521,171;British Pat. 1,146,406; Italian Pat. 799,402; French Pat. 1,521,909;Italian Pat. 800,306; Belgian Pat. 697,727; French Pat. 1,543,001;Belgian Pat. 715,411; Belgian Pat. 717,207.

The layers may also be stabilized in known manner. They may contain theknown plasticizers, wetting agents or hardeners.

After development, processing is carried out in known manner.

EXAMPLE 1 A silver dye bleaching material according to the invention isprepared and processed as follows:

parts of a 1% aqueous solution of6-methyl-4-hydroxy-l,3,3a,7-tetraazaindene, 30 parts of a 0.1%methanolic solution of a red sensitizer according to German 3Auslegeschrift 1,213,240 (Example 11), 250 parts of a 2% aqueoussolution of the blue-green dye:

50 parts of a 7.5% aqueous solution of saponin and parts of a 5%methanolic solution of N,N',N-tris(acryloyl)-perhydrotriazine-l,3,5 areadded successively with stirring at 40 C. into 1000 parts of highlysensitive silver idodobromide emulsion consisting of 8% of gelatin andin which the amount of silver halide present is equivalent to 2.6% ofsilver, 6% of which is in the form of silver iodide. The molar ratio ofsilver to azo bonds is in this case :1 instead of the theoretical ratioof 4:1 based on the bleaching reaction of one azo bond.

The red sensitive emulsion produced in this way is applied to a supportof prepared white pigmented cellulose acetate in such a thickness thatthe layer obtained after drying contains 1.0 g. of silver, in the formof silver halide, per square metre.

Samples of the resulting material are exposed behind a red filter and agrey step wedge which has a logarithmic density increase of 0.10, andthen processed as follows:

(1) Develop 8 minutes in a bath of:

G. N,N-n-butyl-n-w-sulfobutylphenylenediamine 6 Hydroxylamine sulfate 4K Sodium sulfite Potassium bromide 1 Sodium carbonate 100 dissolved inwater to make up 1,000 m1.

(2) Wash 5 minutes. (3) Harden: 5 minutes in a bath of:

Formalin aqueous solution)70 ml. Sodium bicarbonate-5 g. Water up to1,000 ml.

(4) Wash 5 minutes. Bleach dye 15 minutes in a bath of:

Quinoline ml.

Sodium hypophosphite-5 g. Potassium iodide-10 g. Sulfuric acid conc.75ml. Water up to 1,000 ml.

(6) Wash 5 minutes. (7) Bleach-fix 15 minutes in a bath of:

G. Sodium carbonate anhydrous 24 Sodium thiosulfate anhydrous 125Tetrasodium ethylenediaminotetraacetate 26 Ferric chloride 15 Sodiumsulfite anhydrous 13 Water up to 1,000 ml.

(8) Wash 10 minutes.

Sensitometric tests on the resulting dye wedge gives a 7 value of 0.9 atthe maximum density of 1.95. No dye graininess was found on subjectiveviewing of the blue-green dye wedge. Increasing the length of time inthe dye bleaching bath 5 does not alter the given sensitometric values.

If the same material is exposed in the same manner and developed for 5,4, 3, 2 or 1 minutes in a conventional p-methylaminophenol-hydroquinonedeveloper of the following composition:

G. p-Methylarninophenol 1 Hydroquinone 3 Sodium carbonate anhydrous 26Sodium sulfite 13 Potassium bromide 1 Water up to 1,000 ml.

and then treated in baths 2 to 8 as described above, the dye wedgesobtained have 7 values of 3.5, 3.5, 3.5, 3.2 and 2.4 and maximumdensities of 1.68, 1.77, 1.82, 1.88 and 1.92 and very coarse dye grains.

If the developer mentioned under (la) is diluted 1:1 with distilledwater (developer (lb)) and the material which has been exposed in thesame manner is developed in this developer for 5, 4, 3, 2 and 1 minutesand then treated in baths 2 to 8, maximum color densities of 1.90, 1.90and 1.91 and 7 values of 3.1, 3.1 and 2.6 are obtained after 5, 4 and 3minutes development time, respectively. The wedges obtained after 2minutes and 1 minute development cannot be evaluated owing to incompletebleaching. The dye graininess is again distinctly coarser than whenusing the color wedge obtained with developer 1.

In a further experiment, samples of material described are developed ineach case for 10 minutes at 20 C. in developers I to V after exposure asdescribed above. The developer solutions are obtained from the samebasic recipe and contain equimolar quantities of differentpphenylenediamine derivatives. The samples are, after development,treated in baths 2 to 8 for the same lengths of time as given above, themaximum color densities and '7 values shown in Table 1 are obtained.Practically no dye graininess can be found in any case on subjectiveviewing with the naked eye.

Basic solution: G. Sodium salt of ethylenediaminotetraacetate 5 Sodiumsulfite anhydrous 20 Trisodium phosphate 10 Potassium bromide 1 Water upto 1,000 ml.

TABLE 1 Maximum color density 7 Value Developer:

I 1. 06 l. 0 II 1. 0.8 III 1.07 0.7 IV 2. 02 0.8 V 1.83 1. 3

Example 2 40 parts of a 1% aqueous solution of6-methyl-4-hydroxy-l,3,3a,7-tetraazaindene, 40 parts of a 0.1%methanolic solution of green sensitizer 16 given in French Pat.1,531,154 and Belgian Pat. 700,720, 200 parts of a 2% aqueous solutionof the magenta dye of the formula:

30 parts of a 7.5% aqueous solution of saponin and 10 parts of amethanolic solution of N,N',N-tris- (acryloyl)perhydrotriazine-l,3,5 aresuccessively stirred, at 40 0., into 1,000 parts of a highly sensitivesilver iodobromide emulsion which consists of 80 parts of gelatin and 23parts of silver, in the form of silver halide, of which 6 mols percentis in the form of silver iodide. The ratio of silver to azo bonds is inthis case 29:1.

The green sensitive emulsion prepared in this way is applied to thesupport described in Example 1 in such a manner that the layer obtainedafter drying contains 0.90 g. of silver per square metre. Samples of theresulting material are exposed behind a green filter and a grey stepwedge which has a logarithmic density increase of 0.10, and they arethen treated in baths 1 to 8 as given in Example 1 and dried.

Sensitometric determination of the resulting magenta step wedge showedan average maximum color density of 1.3 and a 7 value of 0.95. Again,practically no dye graininess can be seen on subjective viewing with thenaked eye.

If the same material is exposed in the same manner and developed for 5minutes and 1 minute, respectively, in thep-methylaminophenol-hydroquinone developer given under 1a and thenprocessed as described in Example 1, the following figures are obtained:

TABLE 2 Maximum Development eolor time densities 7 Value Minutes Hereagain a distinct dye graininess is found.

If samples of the same material are exposed in the same manner anddeveloped in each case for minutes in developers I to V as described inExample 1 and processed as described in this example, magenta stepwedges which have the maximum color densities and 7 values given inTable 3 are obtained. All the samples obtained in this way have muchless dye graininess than those obtained usingp-methylaminophenol-hydroquinone developer.

TABLE 3 Maximum color densities 7 Value Developer:

Example 3 30 parts of a 1% aqueous solution of 6-methyl-4-hydroxyll,3,3a,7-tetraazaindene, 300 parts of a 2% aqueous solution of theyellow dye of the following formula:

SOaH

blue light, is applied to the support mentioned in Example 1 in such amanner that the layer contains 0.80 g. of silver per square metre afterdrying. Samples of the resulting material are exposed to white lightbehind a grey step wedge which has a logarithmic density increase of0.10 and then treated in baths 1 to 8 according to the example. Thesensitometric measurements showed a maximum color density of 0.98 and a7 value of 0.5. The resulting yellow step wedge is practicallygrainless. If the layer is exposed in the same manner and then developedfor 5 minutes or 1 minute, respectively, in the saidp-methylaminophenol-hydroquinone developer and then treated as describedin Example 1, maximum color densities of 0.94 and 0.96, respectively,and values of 1.8 and 1.6, respectively, and a coarser dye grain isobtained.

EXAMPLE 4 The following layers are applied successively to a support ofprepared white pigmented cellulose acetate:

(1) The red sensitive emulsion given in Example 1 (silver application0.95 g. of silver per m.

(2) A gelatin intermediate layer;

(3) The green sensitive layer given in Example 2 (silver application0.88 g. of silver per m.

(4) A thin intermediate layer of gelatin;

(5 A yellow filter layer of colloidal silver;

(6) A thin intermediate layer of gelatin;

(7) The blue sensitive emulsion layer given in Example 3 (silverapplication 0.78 g. of silver per m?) and ('8) A thin protective layerof gelatin.

The molar ratio of silver to azo bonds in the individual layers is 20:1, 29:1 and 20:1.

Samples of this material are exposed to White light behind a grey stepwedge which has a logarithmic density increase of 0.10, and thenprocessed as follows:

(a) in baths 1 to 8 for the same times as given in Example 1;

(b) 6, 5, 4 and 3 minutes development in p-methylaminophenolhydroquinonedeveloper (1 a) of Example 1 and then treated in baths 2 to 8 as in (a);and

(c) 8 minutes development in developers I to V of EX- zzrggple 1 andthen treated in baths 2 to 8 as in (a) and The following results areobtained:

Maximum Gradacolor than density Graininess (a) Bg 0.75 1.86 Very slight.

Pp 0. 1. 87 Do. Yellow 0. 2.15 Do.

(1)) 6 min. development Bg 2. 4 1.83 Strong. in l 2.3 1. 74 D0. Yellow2. 5 2. 07 Do.

(13) 5 min. development Bg 2.3 1.83 D0. in 1b. Pp 2. 0 l. 81 Do.Yellow.. 2. 4 2. 15 Do.

(1)) 4 min. development Bg 2. 15 1.88 Do. 1n lb. Pp l. 90 1.76 Do.Yellow 2. 15 2. 10 D0.

(11) 3 min. development Bg 2.0 1.92 D0. in 1b. Pp 1. 1. 85 Do. Yellow.2. 15 2. 17 Do.

(c) Developer I Bg 0.6 1. 91 Very slight.

Pp 0.6 1. 96 Do. Yellow 0. 7 2. 17 Do.

(0) Developer lI Bg 0.7 1.85 D0. P 0. 7 1. 94 Do. Yellow. 0. 85 2. 13Do.

(0) Developer III Bg 0. 5 1.94 Do. Pp 0.5 2. 02 D0. Yellow 0. 55 2. 18D0.

(0) Developer IV Bg 0.6 1.90 Do. Pp 0. 6 1.91 Do. Yellow 0.65 2.15 D0.

(0) DeveloperV Bg 1. 25 1. 70 Do. p 1. 25 1. 80 D0. Yellow 1. 35 2. 03Do.

What is claimed is:

1. A process for the production of colored photographic images by thesilver dye bleaching process by exposing a photographic material whichhas at least one silver halide emulsion layer which contains an azo dye,developing, bleaching the dye and bleach-fixing, chracterised in that asilver halide emulsion in which the molar ratio of silver per azo bondof the bleachable azo dye is at least 12:1 is used and that developmentis carried out with a developer of the p-phenylene diamine series whichhas a high sulfite content.

2. A process according to claim 1, characterised in that a silver halideemulsion which has a silver content (in the form of silver halide) of atleast 10 g. per kg. and a molar ratio of silver to dye of 16:1 to 25:1per azo bond is used.

3. A process according to claim 1, characterised in that development iscarried out using a developer which contains, per litre, 0.5 to 25 g. ofa developer substance of the p-phenylene diamine series Which has asulfite content of 15 to 60 g. per litre.

References Cited UNITED STATES PATENTS 2,042,253 5/1936 Gaspar 96-53FOREIGN PATENTS 416,666 9/1934 Great Britain 9653 517,628 2/ 1940 GreatBritain 96-99 J. TRAVIS BROWN, Primary Examiner US. Cl. X.R. 9620 273?UNl'li'ID S'M'Hzs PA'IENI OFFICE 5 s V 1 1 w a v CERTWICA'L l; 01*CURRLL F [ON Dated J 15 1921 Patent No. 3 ,585 ,032

Inventor(s)flrj ch Bockly et a1 It is certified that error appears inthe above-identified patent and that said Letters Patent are herebycorrected as shown below:

Column 1, line 60, "uese" should be use Column 2, line 13, the righthand part of that formula should read as follows:

Signed and sealed this 8th day of February 1972.

(SEAL) Attest:

EDWARD M.FLETCHEB,JR. Attesting Officer ROBERT GOTTSCHALK Commissionerof Patents

